Electrochemical cell systems, such as fuel cell systems have been identified as attractive power supplies for a wide range of applications. Environmental conditions both surrounding the system and proximal to the system can influence the operation and performance of electrochemical cells. Favorable environments in proximity to the electrochemical cells can improve cell performance. As examples, humidity, temperature, mass-transport of reactants, and pollutant or contaminant levels present in the electrochemical cell can affect performance of the cell.
Currently, sub-systems can be integrated into an electrochemical cell system to control operating parameters of the electrochemical cell and provide desired conditions within the electrochemical cell. For example, in some fuel cell systems, external humidification systems, heaters and cooling loops, and reactant delivery pumps and flow fields exist for adjusting internal conditions of the fuel cell. Alternately, fuel cell systems have been designed that minimize use of ancillary components by integrating features for passive control of internal conditions. For example, fuel cells having planar architectures for fuel cells have been developed that provide a passive breathing surface for receiving reactant. Water retention barriers can be used to manage water evaporation from the fuel cells. Conventionally, water retention barriers include porous materials disposed over the active areas and impermeable frames sealed around the perimeter of the fuel cells.
Active control systems can result in substantial parasitic power losses and a larger overall footprint. Further, existing technologies which attempt to passively control internal conditions still exhibit membrane dehydration and significant performance losses. For fuel cells using flow fields, overall performance can be low as a result of uneven water content and localized hot spots across the fuel cell even though a net self-humidifying environment may be possible. For planar fuel cell architectures, evaporation of water from passive breathing surfaces can still cause membrane dehydration, and performance remains limited by insufficient water content in the membrane.